DESCRIPTION (provided by candidate): This proposal outlines a 5-year training program for the candidate to become an independent laboratory-based clinical investigator with research focus on intracellular metabolism of nucleoside analogs in relation to resistance and clinical toxicity. The candidate has completed residency training in Pediatrics and fellowship training in Infectious Diseases. The candidate's goal is to develop a command of virology and pharmacology by the integration of research studies on the cellular pharmacology of HIV reverse transcriptase inhibitors in relation to toxicity in different individuals with the aim of optimizing HIV therapeutic regimens both at the individual and population levels, and a structured curriculum to enhance scientific knowledge in these fields. Dr. Y.C Cheng a renowned cancer and viral pharmacologist will mentor the candidate's scientific development together with co-mentors and an advisory committee of accomplished clinical and scientific investigators with diverse and multidisciplinary backgrounds. The candidate's research objectives are to;i) determine host factors that affect the intracellular NRTI-triphosphate concentration, and ii) determine the contribution of the intracellular NRTI-triphosphate concentration to the development of observed clinical toxicities. Specific aim 1 is to determine the effect of host factors on the metabolism of nucleoside analogs in human PBMCs. In specific aim 2 the individual differences in phosphorylation of these nucleosides will be studied using state-of-the-art ELISA technique. The sensitivity of the ELISA will be assessed using HPLC as gold standard. Specific aim 3 is to determine the association among intracellular triphosphate concentration, mitochondria! DNA concentration, and development of clinical or laboratory toxicity in HIV-infected individuals on NRTI-based regimens. The anticipated results from above studies will impact on optimization of HIV therapeutics and inform on the mechanisms of clinical toxicities associated with nucleoside analog usage. The novelty of the ELISA is to overcome, with respect to current HPLC methods, lack of sensitivity and the labor intensive nature. This will provide a quick and rapid technique for PK-PD studies to make it possible to screen large populations, and secondly, has a potential for therapeutic drug monitoring of HIV-1 patients and optimization of individual therapy especially in persons who are heavily treatment-experience with clinical toxicities.